Ultrasonic diagnostic imaging with cordless scanhead transmission system

ABSTRACT

An ultrasonic diagnostic imaging system is provided with cordless scanheads which wirelessly transmit ultrasonic image signals to the imaging system. The transmitted image signals are accompanied by header and trailer information which identify display characteristics of the image signals for accurate processing and display by the ultrasound system, and also delineates discrete units of information such as data for a complete scanline or image frame. Communication protocol headers and trailers are described which define the communication and coding protocols for the transmitted ultrasound information.

This invention relates to ultrasonic diagnostic imaging systems and, inparticular, to ultrasonic diagnostic imaging systems in which thescanning of patients is done by cordless scanheads.

Ultrasonic diagnostic imaging systems have traditionally been thought ofas having two major constituent parts: a probe or scanhead, and themainframe processor or system. The probe contains the piezoelectrictransmitter and receiver of ultrasonic energy which is used to scan thepatient's body. The system contains the sophisticated electroniccontrollers and processors which control the probe and turn the receivedecho signals into diagnostic images and information. But there is oneadditional ever-present component: the cable which connects the probe tothe system, through which power and signals are coupled between theprobe and system.

The probe cable has taken many forms as it has evolved over the years,and has had varying impacts on physician and patient comfort andconvenience. Early products which only were used for audio Doppler orA-line (single line) imaging needed very few wires in the cable. Sincethe probes for such products generally used single element or singlepiston transducers, sometimes referred to as "pencil probes," signal andground wires often sufficed as a complete cable. Such a probe had anunsteered, fixed focus along a single beam. The user adjusted the probeby physically moving it to a different position or offsetting it fromthe body with an acoustic standoff. While the thin, light cable wasconvenient to lift and maneuver, the caliber of the diagnosticinformation obtained was minimal.

The advent of B arm systems took convenience in a different direction.In these systems the probe was attached to the end of an articulated armwhich provided probe position information for two dimensional imaging.The step-up in diagnostic image quality was at the expense of thearticulated arm, which constrained imaging to its range of movement.Merged into the articulated arm, the cable was virtually unnoticeable inthe ungainly mechanism.

Greater freedom of movement returned with the development of themechanical sector scanner probe. The mechanical sector scanneroscillated the transducer back and forth to scan the image field, andthe oscillating mechanism provided the spatial orientation for twodimensional imaging. A single piston transducer with two wires, signaland ground, was needed, as well as wires to power and control theoscillating mechanism and send the spatial orientation signals to thesystem. The hand-held probe was convenient, but the cable was beginningto grow in size.

Cable growth accelerated considerably with the advent of solid-state orarray probes. In the array probes the transducer comprises an array ofdozens or hundreds of elements which are individually controlled toelectronically steer and focus the ultrasound beam. But with individualcontrol comes the need for individual wires: a 128 element transducerprobe can require a cable with 128 individual wires. Since received echosignals are generally of very low levels, the wires are not simplystranded wires, but coaxial lines, each with its own signal line andconductive shield. While various multiplexing schemes in the probe havebeen used to reduce the number of wires in the cable, these schemes canhave adverse consequences for performance criteria such as frame rate,aperture size, and control complexity. Accordingly it would be desirableto reduce the size of the probe cable, or even eliminate it, therebyimproving clinician and patient convenience but without incurring anyperformance penalties.

In accordance with the principles of the present invention, anultrasonic diagnostic imaging system is presented in which the probecable is eliminated, giving rise to the utmost convenience for theclinician and patient. This convenience is brought about by theinclusion of a wireless transmitter in the probe case, eliminating theneed to connect the probe to the mainframe ultrasound system. Theultrasound system includes a receiver for receiving the ultrasoundinformation from the probe. The transmission of signals from the probeto the ultrasound system is formatted in accordance with the presentinvention so that the ultrasonic image information acquired andtransmitted by the probe is reliably and accurately reproduced in animage displayed on the ultrasound system.

In the drawings:

FIG. 1 illustrates in block diagram form the conventional configurationof an ultrasonic probe, cable, and ultrasonic imaging system;

FIG. 2 illustrates an ultrasonic probe with an integral beamformeroperatively connected to an ultrasonic imaging system;

FIG. 3 is a more detailed block diagram of the ultrasonic probe of FIG.2;

FIG. 4 illustrates in block diagram form a digital beamformingintegrated circuit suitable for use in the ultrasonic probe of FIG. 3;

FIG. 5 illustrates in block diagram form a multiplexer suitable for usein the ultrasonic probe of FIG. 3;

FIGS. 6a and 6b illustrate a cable-less embodiment of the ultrasonicprobe of FIG. 3 and an ultrasonic imaging system in accordance with theprinciples of the present invention; and

FIGS. 7a and 7b illustrate data transmission formats for the cable-lessultrasonic probe of FIG. 6a.

Referring first to FIG. 1, a conventional ultrasonic probe, cable andimaging system arrangement is shown in block diagram form. Theultrasonic probe 10 includes a transducer array 12. Conductors 14connect individual elements of the transducer array to conductors insidea cable 20, which connects to an ultrasonic imaging system 30. Theconductors of the cable are electrically connected to a beamformer 32 inthe imaging system, which controls the timing of the pulsing of theelements of the transducer array, and delays and sums received echosignals from the transducer elements to form coherent beams of echosignals. The beamformed echo signals are coupled to an image processor34 where they are processed to form an image of tissue or flow withinthe body of the patient being scanned. The resultant ultrasonic image isdisplayed on an image display 36. Coordination of the processing anddata flow of the beamformer 32 and image processor 34 is provided by asystem controller 38, which receives instructions from a user by way ofvarious user controls.

While the elements of the transducer array 12 are shown directly wiredto the conductors of the cable in FIG. 1, multiplexers can be includedwithin the probe between the array elements and the cable to reduce thenumber of cable conductors. It is then necessary to control themultiplexers from the ultrasound system with control lines, so that thecable conductors are multiplexed to the elements of the current activeaperture each time the probe is transmitting or receiving ultrasonicsignals.

FIG. 2 illustrates an ultrasound system in which the beamforming forboth ultrasonic transmission and reception is done within the probe,significantly reducing the number of conductors needed within the cable20. The elements of the transducer array 12 are coupled to atransmit/receive beamformer 16, which controls the timing, steering andfocusing of the ultrasonic beams transmitted by the array and thebeamforming of coherent echo signals from the signals received by thearray elements. The formed beam, rather than signals from eachtransducer element, are coupled through the cable 20 for imageprocessing and display by the ultrasound system 30. The cable 20 willalso convey control information from the system controller 38 whichcommands the beamformer as to the specifics of the image being scanned.This control information can be conveyed by a serial digital line in thecable and the information stored in beamformer registers as discussedbelow. The cable will also carry supply voltages for the beamformer andthe transducer array. Even when the transmit/receive beamformer 16 is adigital beamformer producing multibit digital data, the number of cableconductors is still substantially reduced as compared to the conductorsrequired for a conventional 64, 96 or 128 element transducer array.

Since the received ultrasound beam is formed in the probe 10 in FIG. 2,the probe does not need to use the beamformer 32 in the ultrasoundsystem 30. The beamformed echo signals produced by the probe 10 can becoupled directly to the image processor 34 for immediate processing andsubsequent display. In the embodiment of FIG. 2 this is accomplished bya switch S which is switched under control of the system controller toconnect the beamformed echo signals from probe 10 to the imageprocessor, rather than signals produced by the system beamformer 32. Asis conventional, a "personality chip" in the probe 10 or its systemconnector 22 notifies the user of the characteristics of the probe 10and selection of probe 10 by the user at the user controls causes thesystem controller to command the probe to operate and connect its echoinformation to the image processor 34.

FIG. 3 illustrates an embodiment of an ultrasonic probe with abeamformer 16 and a transmit/receive multiplexer/demultiplexer 18. Thebeamformer 16 includes transmit and timing circuitry 300 which controlsthe timing of the ultrasonic waves transmitted by the elements of thetransducer array 12. The transmit and timing circuitry receives commandsignals from the ultrasound system 30 to control the probe to producethe type of image desired by the user. The transmit and timing circuitryalso directs the transmit/receive multiplexer/demultiplexer to selectthe desired active aperture of the array. The transmit and timingcircuitry can also control the nature of the transmitted wave, forinstance, transmitting different waves for B mode and Doppler imaging.The timing and control signals are applied to themultiplexer/demultiplexer 18 and elements of the array are excited atthe proper times to steer and focus the desired transmit beam.

Echoes received by the array elements are converted to electricalsignals by the elements and directed by the multiplexer/demultiplexer 18to the receive beamforming circuitry of the beamformer 16. The receivedecho signals from the transducer elements of the active receive apertureare coupled to individual channels of the beamformer; the drawing ofFIG. 3 illustrates a four channel beamformer. The preferred beamformeris fabricated in integrated circuit form and preferably will contain amultiple of four channels in each beamformer chip. Four, eight, orsixteen channel beamformer chips may readily be employed for most largeelement count arrays. The preferred beamformer is a sampled databeamformer which may use either sampled analog or digital technology. Ineither case each channel of the beamformer includes an initialquantizing stage 31 followed by a delay line stage 32. The outputs ofthe delay line stages are coupled to a summing circuit 320 whichcombines the delayed echo signals to form the receive beam. The fourchannel beamformer illustrated in FIG. 3 includes four quantizing stagesQ₁, Q₂, Q₃, and Q₄ followed by four delay line stages DL₁, DL₂, DL₃, andDL₄. The coherent echo signals at the output of the summing circuit 320are coupled to the ultrasound system 30 for image processing anddisplay.

When the receive beamformer is of the sampled analog variety thequantizing stages comprise sample-and-hold circuits which sample thereceived echo signals at times indicated by the transmit and timingcircuitry 300. The sampled analog signal voltages are then appropriatelydelayed by charge coupled device (CCD) bucket brigade delay lines as thedelay line stages. The delay time is controlled by the transmit andtiming circuitry 300 in any of several ways. One is to select one of aplurality of input taps to the CCD delay line to which the sampledvoltage is applied. Another is to select one of a plurality of outputtaps from the stages of the CCD delay line to the summing circuit 320.In either case the selection of the tap will select the number of stagesthrough which the voltage sample will be shifted and hence delayed. Athird delay technique is to vary the frequency at which samples areshifted through the CCD stages: a lower frequency imparts a longer delayto the samples being shifted. The summed output signals may be digitizedby an analog to digital converter in the probe and transmitted to theultrasound system 30 in digital form, or the analog signals may betransmitted to the ultrasound system 30 and converted into digital echosamples in the ultrasound system. The latter approach would require onlya single output signal conductor in the cable 20.

When the receive beamformer is a digital beamformer, the quantizingstages comprise analog to digital converters which convert the perelement analog signals to digital samples at sampling times indicated bythe transmit and timing circuitry 300. The digital echo samples are thendigitally delayed by a digital delay line which can take the form of arandom access memory, shift register, or digital FIFO register. Thedelay of each digital delay stage is controlled by the transmit andtiming circuitry 300 which controls the write-read interval of a samplein memory or the shift frequency of a shift register or FIFO register.The delayed samples at the outputs of the digital delay lines aredigitally summed and forwarded to the ultrasound system 30.

A digital beamformer suitable for use in the probe of FIG. 3 is shown inblock diagram form in FIG. 4. This drawing shows one section 16a of abeamformer integrated circuit 16. There are eight such sections on thebeamformer I.C. to provide beamforming of the signals of eighttransducer elements from the multiplexer/demultiplexer 18. Each echosignal from the multiplexer/demultiplexer is coupled to the input of anA/D converter 310, where the echo signals are converted to digital data.The A/D converters are located on the same integrated circuit as thebeamformer itself, which minimizes the external connection pins of theintegrated circuit. Only one analog input pin is required for eachbeamformer channel, and only one set of digital output pins is requiredfor the coherently summed output signal. The digital data from the A/Dconverter for each element (or each pair or group of elements in afolded or coarse aperture) is shifted into a first in, first out (FIFO)register 312 by a clock signal A/D CLK. The A/D CLK signal is providedby a dynamic focus controller 314 which defers the start of the clocksignal to provide an initial delay, then controls the signal samplingtimes to provide dynamic focusing of the received echo signals. Thelength of the FIFO register 312 is determined by the transducer centerfrequency, the aperture size, the curvature of the array, and the beamsteering requirement. A higher center frequency and a curved array willreduce the steering delay requirement and hence the length of the FIFOregister, for instance. The delayed echo signals from the FIFO register312 are coupled to a multiplier 316 where the echo signals are weightedby dynamic weight values provided by a dynamic weight controller 318.The dynamic weight values weight the echo signals in consideration ofthe effects of the number of active elements, the position of an elementin the aperture, and the desired apodization function, as the apertureexpands by the inclusion of additional outer elements as echoes arereceived from increasing depths along the scanline. The delayed andweighted echo signals are then summed with appropriately delayed andweighted echo signals from other elements and echo signals from anyother delay stages which are coupled in cascade through a summer 320.The beamformed echo signals, together with synchronous overflow bits,are produced as output scanline data on an RF data bus. Accompanyingeach sequence of scanline echo signals is identifying informationprovided by an RF header sequencer on the I.C., which identifies thetype of scanline data being produced. The RF header can identify thescanline as B mode echo data or Doppler data, for instance.

Other digital and sampled data storage devices can be used to providethe beamformer delays, if desired. A dual ported random access memorycan be used to store the received digital echo samples, which are thenread out from the memory at times or in sequences which provide thedesired delay for the signals from the transducer elements.

Each section 16a of the beamformer I.C. includes transmit controlcircuits 302-308 for four transducer elements of the array. The eightsections of the I.C. thus provide transmit control for 32 elements ofthe array at the same time, thereby determining the maximum transmitaperture. The transmit control circuits produce waveforms ofpredetermined durations and periodicities which activate multiplexerpulsers at the appropriate times to produce a transmitted acousticsignal which is steered in the desired direction and focused at thedesired depth of focus.

The beamformer I.C. 16 includes a common control section 330 whichprovides overall control for the transmission and receive functions ofthe eight beamformer channels on the I.C. The control section 330 iscontrolled by and receives data under control of the system controller38 located in the ultrasound system 30. The control data tables for aparticular image frame are stored in memory in the ultrasound system andare loaded into the control section 330 under command of the systemcontroller. The control section 330 includes a number of sequencers forthe probe's transmit and receive functions. The frame sequencer 332produces information used by other sequencers which identifies the typeof image frame which is to be produced. The frame sequencer may, forexample, be loaded with data that defines the next frame as B modescanlines interspersed between groups of four Doppler scanlines, andthat the sequence of scanlines will be all odd numbered scanlinesfollowed by all even numbered scanlines. This information is supplied tothe line sequencer 334, which controls the timing required to acquirethe desired scanlines. During the scanline acquisition the linesequencer controls the TGC sequencer 336 so that it will produce thedesired sequence of TGC control data. The TGC control data from the TGCsequencer is converted to a voltage signal by a digital to analogconverter (DAC) 338 and applied to the TGC control input terminal(s) ofthe multiplexer/demultiplexer 18. The address sequencer 342 controls theloading of data for a new scanline into various realtime registers ofthe beamformer such as the registers of the TGC sequencer, the dynamicfocus 314 and dynamic weight controllers 318, and the serial bussequencer 340, which produces serial data on a serial bus for controlregisters of the multiplexer/demultiplexer 18. All registers on thebeamformer I.C. which perform real time functions are double buffered.The registers of the transmit/receive multiplexer/demultiplexer 18 arealso double buffered so that control data for multiplexing and TGCcontrol can be put on the serial bus and loaded intomultiplexer/demultiplexer registers during the line preceding thescanline for which the control data is used.

The beamformer I.C. includes in its control section a clock generator350 which produces a plurality of synchronous clock signals from whichall operations of the probe are synchronized. A crystal oscillator (notshown) is coupled to the beamformer I.C. 16 to provide a basic highfrequency such as 60 MHz from which all of the clock signals of theprobe may be derived.

Further details on the operation of the beamformer I.C. and itssequencers may be found in U.S. Pat. No. 5,817,024.

A transmit/receive multiplexer I.C., suitable for use asmultiplexer/demultiplexer 18 in the probe of FIG. 3, is shown in FIG. 5.The signal paths of the multiplexer I.C. 18A are divided into fouridentical sections S1, S2, S3, and S4. In this drawing section S1 isshown in internal detail. The section S1 includes two 2:1 transmitmultiplexers 408 and 410, each of which is responsive to a pulser signalon one of eight Transmit In lines. Each 2:1 transmit multiplexer has twooutputs which drive pulsers 402, 404, and 414, 416, the outputs of whichare coupled to multiplexer I.C. pins to which transducer elements areconnected. In the illustrated embodiment the 2:1 transmit multiplexer408 is coupled to drive either element 1 or element 65, and the 2:1transmit multiplexer 410 is coupled to drive either element 33 orelement 97. The 2:1 transmit multiplexers of the other sections of themultiplexer I.C. 18A are each similarly coupled to four transducerelements. With a separate pulser for each transducer element, themultiplexer I.C. 18A can independently and simultaneously drive eight ofthe sixteen transducer elements to which it is connected.

The transducer element pins to which the pulsers of each section arecoupled are also coupled to the inputs of a 4:1 receive multiplexer andswitch 412. When the pulsers are driving the transducer elements duringultrasound transmission, a signal on a Transmit On line which is coupledto all of the 4:1 Receive Multiplexers and Switches on the multiplexerI.C. switches them all into a state which presents a high impedance tothe high voltage drive pulses, thereby insulating the rest of thereceive signal paths from these high voltage pulses. All of the 4:1receive multiplexers and switches of the multiplexer I.C. are alsocoupled to a Receive Test pin of the multiplexer I.C., by which a testsignal can be injected into the receive signal paths and propagatethrough the receiver system. During echo reception each 4:1 receivemultiplexer and switch couples the signals of one of the four transducerelements to which it is coupled to a 1:16 multiplexer 418 by way of afirst TGC stage 422. The gain of the first TGC stages on the multiplexerI.C. is controlled by a voltage applied to a TGC1 pin of the multiplexerI.C. which, in a constructed embodiment, comprises two pins forapplication of a differential control voltage. The 1:16 multiplexers ofeach section of the multiplexer I.C. each route received echo signals toone of the sixteen lines of a Sum Bus 440. Two of the sixteen Sum Buslines are shown at the right side of the drawing, and are coupled tofilter circuits 222. The filtered bus signals are coupled to input pinsleading to two second TGC stages 424 and 426, the gain of which iscontrolled by the voltage applied to one or two TGC2 pins. The outputsof these second TGC stages in the illustrated embodiment are connectedto output pins leading to channels of the probe's beamformer I.C.

The multiplexer I.C. 18A also includes a control register 430 whichreceives control signals over a serial bus from the beamformer I.C. Thecontrol register distributes control signals to all of the multiplexersof the multiplexer I.C. as shown by the Ctrl. input arrows.

Constructed embodiments of the multiplexer and beamformer I.C.s willhave a number of pins for supply and bias voltages and groundconnections and are not shown in the drawings.

It will be appreciated that only a few conductors are needed in theprobe cable in the embodiments of FIGS. 2-5 since the numerousconductors for individual transducer elements are replaced by conductorsfor the beamformer control data, the beamformed output signals andsupply voltages for the transducer, beamformer and multiplexer I.C.s. Atypical CCD embodiment can require a conductor for the CCD beamformeroutput signals, a serial data line providing control data from theultrasound system to the transmit and timing circuitry 300, DC supplyvoltages and reference conductors for the beamformer and multiplexerI.C.s, and a drive voltage as required to drive the piezoelectricmaterial during ultrasound transmission. The digital beamformerembodiment would replace the CCD output conductor with a number ofconductors equal to the number of bits in a beamformed data word (forparallel transmission) or a serial data line if the beamformed words arebeing sent to the ultrasound system as serial data. Parallel outputdata, while requiring more conductors in the cable, affords a worthwhileimprovement in axial resolution and eliminates the need for a serial toparallel converter in the ultrasound system.

The present inventors have discovered that since an ultrasound probe ofthe present invention is producing beamformed scanline samples as outputsignals rather than individual signals from a large number of transducerelements, the volume of data produced by the probe is at a level whichwill permit wireless transmission of the probe's output signals to theultrasound system. A transmitter bandwidth of 4 M bits per second issufficient to transfer ultrasound images without compression at a framerate of nearly 15 Hz, suitable for real time image display. I.C.transmitter bandwidths today are in the range of 11 MBPS, and areexpected to be in the range of 25 MBPS in a few years. Additionally, bythe use of data compression, the number of bits per B mode ultrasoundimage, around 250,000 bits per image, can be reduced with minimaldecrease in image quality by data compression factors ranging from 4 to20, affording greater frame rates. An embodiment of the presentinvention which provides this cable-less connection to an ultrasoundsystem is shown in FIGS. 6a and 6b.

In FIG. 6a the probe of FIG. 3 includes several additional elementscoupled to the beamformer 16, a digital signal processor 52 whichperforms filtering and detection, a compression/decompression circuit(CODEC 54) which compresses the beamformed data, a double buffered framestore 56, and a transceiver 50 which communicates with a similartransceiver in the ultrasound system 30. The CODEC 54 is capable ofimplementing several compression schemes, including JPEG, MPEG andwavelet compression techniques, as described in concurrently filed U.S.patent application Ser. No. 09/197,398, entitled "ULTRASONIC DIAGNOSTICIMAGING SYSTEM WITH CORDLESS SCANHEADS." The elements 50-56 are operatedunder control of a microcontroller 200 which controls the processing andtransmission of data to and from the ultrasound system. Useful asmicrocontrollers are processors such as the Intel 80186 processor andcomparable contemporary processors available from vendors such asHitachi and Intel. The transceiver 50 receives control data from theultrasound system to control the type of ultrasound image beingproduced, such as a B mode or Doppler image, and the size of a Dopplerwindow in a colorflow image, for instance. As this control data isreceived it is coupled to the transmit and timing circuitry 300 tocontrol the scanning performed by the probe.

The scanline data produced by the summer 320 is coupled to the digitalsignal processor 52 which performs filtering and, optionally, detection.The DSP 52 can also perform Doppler processing as described in theaforementioned U.S. Pat. No. 5,817,024. The filtering performed can beeither lowpass or bandpass filtering which removes sampling frequencysignal components from the beamformed signals. Preferably this filteringis implemented by multiplier-accumulators performing quadrature bandpassfiltering (QBPs). As described in U.S. patent application Ser. No.08/893,426, such an implementation advantageously performs threefunctions: bandlimiting the beamformed signals, separating the signalsinto quadrature (I and Q) pairs, and decimating the sampling rate. In apreferred embodiment the transducer signals are oversampled by thequantizing stages of the beamformer in relation to the Nyquistcriterion. Oversampling permits the filtering of the beamformed signalsby decimation filtering which both imposes a filter characteristic onthe signals and reduces the data rate. The reduced data rate has thebenefit of lessening the data transfer requirement for the transceiverin a wireless probe.

B mode signals can be detected in the DSP by taking the square root ofthe sum of the squares of the I and Q samples. For Doppler signals the Iand Q data can be wall filtered by the DSP and, through storage of agroup of received scanlines forming a Doppler ensemble, Dopplerfrequency estimation can be performed at sample volume points along eachscanline. The ultrasound signal data may be compressed if desired by theCODEC 54 and is stored temporarily in the frame store 56. At the timewhen the microcontroller 200 determines that the ultrasound data is tobe transmitted to the ultrasound system 30, the data is coupled to thetransceiver 50 for transmission back to the ultrasound system for imageprocessing and display. Since image processing including scan conversionis performed in the ultrasound system, the scanlines are transmitted tothe ultrasound system in unscanconverted form, e.g., R-θ format. Theimage processor 34 in the ultrasound system converts the R-θ scanlinedata to the desired display format.

Since the cable-less probe of FIG. 6a does not receive power by theusual cable, the probe must be battery powered. A battery and powerdistributor subsystem 60 is shown as a component of the probe. Thesubsystem 60 preferably uses rechargeable lithium ion batteries andproduces supply voltages for the circuitry and transceiver of the probeand the requisite excitation voltage for the piezoelectric elements ofthe transducer array. Techniques for recharging the battery from theultrasound system are described in concurrently filed application Ser.No., entitled "ULTRASONIC DIAGNOSTIC IMAGING SYSTEM WITH CORDLESSSCANHEAD CHARGER."

The ultrasound system 30 of FIG. 6b includes a transceiver 50 for thetransmission of scan control data to the probe of FIG. 6a and for thereception of ultrasonic image data from the probe. The scan control datais provided to the system transceiver 50 by the system controller 38.The received image data bypasses the beamformer 32 in the ultrasoundsystem since it has already been beamformed in the probe, and is applieddirectly to the image processor 34 for image processing and display.

Transceiver configurations suitable for use in the probe of FIG. 6a aredescribed in concurrently filed U.S. patent application Ser. No.09/197,398, entitled "ULTRASONIC DIAGNOSTIC IMAGING SYSTEM WITH CORDLESSSCANHEADS."

FIGS. 7a and 7b illustrate two possible transmit data sequences by whichbeamformed image data can be transmitted by the probe transceiver ofFIG. 6a to an ultrasound system 30. Other formats may be employed whencommunicating to platforms other than ultrasound systems, such ascomputers and data storage devices. As FIG. 4 showed, the illustratedbeamformer I.C. includes an RF header sequencer 344 which is capable ofinserting identifying header information in the sequence of scanlinedata. One way this header information can be employed is shown in FIG.7a. In this embodiment a frame of scanline data is preceded by a frameheader which provides the ultrasound system with information about thescanline data which is to follow. This may include information as to thenumber and type of scanlines in the frame, for instance, and the type ofcompression employed, if any. The frame header is then followed by thescanline data for the scanlines in the frame. Optionally the sequence offrame data may be ended by a frame trailer. At the beginning and,optionally, at the end of the data sequence are protocol headers andtrailers which identify the communication protocols used, such as TCP/IPand other lower level data. These transmission protocols can be expectedto impose about 7-8% overhead on the transmit bandwidth under conditionsof interference-free reception.

FIG. 7b illustrates a second scanline transmit format in which the RFheader sequencer inserts a header before each scanline of the image. Asthe drawing shows, the scanline 1 data is preceded by a header for line1, the scanline 2 data is preceded by a header for line 2, and so on.Each line header provides identifying information about its associatedscanline, such as its spatial location in the image and whether it is aB mode or Doppler scanline.

It will be appreciated that a combination of these two formats may alsobe used, that is, transmitting a frame header at the start of each imageframe and a line header for each scanline of the frame. Prior to thecommencement of transmission of ultrasonic image data the probe willtransmit basic identifying information to the ultrasound system, such asthe identity of the type of probe (e.g., 4 MHz curved array type), theformat of the data which will be transmitted by the probe, bandwidth, ofthe ultrasound data, unique functions of the probe, deficiencies of theprobe (e.g., a failed array element), functional characteristics (e.g.,the gain characteristic across the probe channels, temperature data),and other operating characteristics of the probe which may be useful forthe ultrasound system. The ultrasound system can respond to thisinformation with setup and checkout information of its own to establishoperation of the probe before commencing actual image scanning anddisplay. Important safety information, such as probe temperature duringan overheating condition, would be transmitted to the system as requiredon an interrupt basis to inform the user of the potential hazard by, forinstance, an alert displayed on the monitor, and the probe can theneither be commanded to power down by the ultrasound system or canself-execute a power-down.

What is claimed is:
 1. An ultrasonic probe which wirelessly communicateswith an ultrasound system for display of ultrasonic information acquiredby said probe, said probe comprising:a multielement transducer arraywhich produces ultrasonic image information signals in response toreceived ultrasonic echoes; a source of header data providinginformation characterizing said ultrasonic image information signals;and a transmitter, responsive to said ultrasonic image informationsignals and said source of header data which wirelessly transmitsultrasonic image information and header data, wherein said ultrasoundsystem includes a receiver for receiving said transmitted ultrasonicimage information and said header data for display of said ultrasonicimage information on the basis of said characterizing information. 2.The ultrasonic probe of claim 1, wherein said transmitter transmits saidultrasonic image information signals as sequences of scanline data, andwherein said header data contains information characterizing individualscanlines.
 3. The ultrasonic probe of claim 1, wherein said transmittertransmits said ultrasonic image information signals in sequences ofimage frame data, and wherein said header data contains informationcharacterizing an image frame.
 4. The ultrasonic probe of claim 1,wherein said transmitter transmits said ultrasonic image informationsignals in sequences of scanline data of an image frame, and whereinsaid header data contains information characterizing the number and typeof scanlines in an image frame.
 5. The ultrasonic probe of claim 4,wherein the types of scanlines in an image frame are B mode scanlines,Doppler scanlines, or both.
 6. The ultrasonic probe of claim 1, whereinsaid probe further includes a compression circuit for compressingultrasonic image data prior to transmission,wherein said header datacharacterizes the compression characteristics applied to said ultrasonicimage data.
 7. The ultrasonic probe of claim 1, further comprising asource of communication protocol data providing informationcharacterizing the type of data transmission employed by saidtransmitter,wherein said transmitter is further responsive to saidsource of communication protocol data for wirelessly transmitting saidprotocol data for reception by said ultrasound system receiver.
 8. Theultrasonic probe of claim 1, wherein said header data comprisesinformation identifying the spatial origin of said ultrasonic imageinformation signals.
 9. The ultrasonic probe of claim 8, wherein saidtransmitter transmits said ultrasonic image information signals assequences of scanline data, and wherein said header data containsinformation identifying the spatial origin of individual scanlines. 10.The ultrasonic probe of claim 1, wherein said probe further includes asource of temperature information concerning said probe, and whereinsaid transmitter further transmits said temperature information to saidultrasound system receiver.
 11. The ultrasonic probe of claim 10,wherein said probe further includes an overtemperature shutdown circuit,responsive to said temperature information, which shuts down said probein the event of an overtemperature condition.
 12. The ultrasonic probeof claim 10, wherein said probe further includes an overtemperatureshutdown circuit, responsive to a command from said ultrasound system,which shuts down said probe in the event of an overtemperaturecondition.
 13. The ultrasonic probe of claim 1, wherein said transmittertransmits said ultrasonic image information signals in sequences ofscanline data which together comprise an image frame, and wherein saidheader data contains information characterizing said image frame andindividual scanlines in said image frame.
 14. The ultrasonic probe ofclaim 1, further comprising a source of data providing informationcharacterizing said probe,wherein said transmitter is further responsiveto said source of probe characterizing data for wirelessly transmittingsaid probe characterizing data for reception by said ultrasound systemreceiver.
 15. The ultrasonic probe of claim 14, wherein said probecharacterizing data is transmitted by said transmitter prior to thetransmission of said ultrasonic image information signals.
 16. Theultrasonic probe of claim 14, wherein said probe characterizing datacomprises data characterizing said transducer array.
 17. The ultrasonicprobe of claim 1, wherein said header data is transmitted by saidtransmitter prior to the transmission of the ultrasonic imageinformation to which it relates.
 18. The ultrasonic probe of claim 1,wherein said ultrasonic image information is transmitted by saidtransmitter prior to the transmission of the header data to which itrelates.
 19. The ultrasonic probe of claim 18, wherein said header datais contained in a trailer.
 20. An ultrasonic probe which wirelesslycommunicates with an ultrasound system for display of ultrasonicinformation acquired by said probe, said probe comprising:a multielementtransducer array which produces ultrasonic image information signals inresponse to received ultrasonic echoes; a source of header dataproviding information characterizing said ultrasonic image informationsignals; a source of trailer data corresponding to said header data; anda transmitter, responsive to said ultrasonic image information signalsand said sources of header and trailer data which wirelessly transmitsultrasonic image information preceded by header data and followed bytrailer data, wherein said ultrasound system includes a receiver forreceiving said transmitted ultrasonic image information and said headerand trailer data for display of said ultrasonic image information on thebasis of said characterizing information.
 21. The ultrasonic probe ofclaim 20, wherein said header data comprises information characterizingan ultrasonic image frame; and wherein said trailer data comprises aframe trailer.
 22. The ultrasonic probe of claim 20, wherein said headerdata comprises information characterizing the transmission protocol forsaid ultrasonic image information; and wherein said trailer datacomprises a protocol trailer.
 23. The ultrasonic probe of claim 20,wherein said header data comprises information characterizing andultrasonic image frame and the transmission protocol for said ultrasonicimage information; and wherein said trailer data comprises a frametrailer and a protocol trailer.
 24. An ultrasonic probe which wirelesslycommunicates with an ultrasound system for display of ultrasonicinformation acquired by said probe, said probe comprising:a multielementtransducer array which produces ultrasonic image information signals insequences of scanline data in response to received ultrasonic echoes; asource of header data providing information characterizing saidultrasonic image information signals and information characterizing awireless communications protocol; a source of trailer data correspondingto said header data; and a transmitter, responsive to said ultrasonicimage information signals and said sources of header and trailer datawhich wirelessly transmits a communications protocol header, sequencesof scanline data preceded by ultrasonic image information headers, and acommunications protocol trailer, wherein said ultrasound system includesa receiver for receiving said transmitted ultrasonic image informationand said header and trailer data for display of said ultrasonic imageinformation on the basis of said characterizing information.
 25. Theultrasonic probe of claim 24, wherein the sequences of scanline datawhich are transmitted following a communications protocol header andpreceding an associated communications protocol trailer comprise thescanline data of an ultrasonic image frame.